Laryngoscopes are used by doctors and surgeons for viewing the larynx and for endrotracheal intubation. Visualization of the larynx is therefore necessary for passing a tube through the larynx into the trachea. Such endotracheal intubation is usually employed in the administration of anesthesia for the passage of anesthetic gases, vapors and oxygen. Also, the tube helps to keep the airway open and prohibits the patient's tongue from falling down and obstructing the air passage. The tube is also helpful for the anesthesiologist to ventilate the patient manually or mechanically. Endotracheal intubation is also useful in resuscitating patients from cardiac arrest and other emergencies. Therefore, exposure of the larynx with the aid of a laryngoscope is necessary for most endotracheal intubation.